Arc suppressing plates and hood for electric switches



D. F. DALY July 10, 1962 ARC SUPPRESSING PLATES AND HOOD FOR ELECTRIC SWITCHES Filed May 24, 1960 3 INVENTOR.

Dan/e/ 00/y BY his afforneys Unitcd States Patent 3,043,938 ARC SUPPRESSING PLATES AND HOOD FOR ELECTRE SWITCHES Daniel F. Daly, Hartford, Conn., assignor to The Arrow- Hart & Hegernan Electric Company, Hartford, Conn.,

a corporation of Connecticut Filed May 24, 196i), Ser. No. 31,407 10 Claims. (Cl. 200-144) This application is a continuation-in-part of my copending application Serial No. 825,746, now abandoned, filed July 8, 1959.

This invention relates to means for suppressing arcs incident to the separation of contacts in an electric switch. More particularly, it relates to novel are snufiing plates for use in connection with an arc hood or shield for controlling or directing the movement of the arc and are products.

Various devices have been known and used in electric switches to control and direct the arcs incident to contact separation. Many of such devices have been of complicated and expensive form. Particular circumstances required different treatment and diiferent constructions for handling the arcs drawn during contact separation in different types of electric switches. The present invention was devised particularly for use with knife-blade switches of the multi-pole type; but the invention is not limited to such use.

An object of the invention is to provide a simple economical arc snufi'ing plate structure which can be easily assembled in an arc hood or shield in such fashion as to cause the arc to move rapidly over the cool surfaces of the contact until it is extinguished while at the same time confining, insofar as possible, the are within the shield while permitting the blowing out of the hot arc gases.

Another object of the invention is to provide an arc plate assembly in an arc shield or hood which will limit the blowing out therefrom of the debris resulting from the are so as to confine the debris to the hood, mainly, and reduce the blowing of burnt particles or products of the arc onto the walls or adjacent parts of the switch housing or enclosure.

Other objects and advantages of the invention will appear as it is described in connection with the accompanying drawings.

In the drawings:

FIG. 1 is a side elevation view showing diagrammatically a fixed contact and a movable contact blade in current-carrying position and also at the instant of separation.

'FIG. 2 is a plan view of the arc suppressing plate of the present invention showing diagrammatically the are at the instant of contact separation and in another position after it has moved.

FIG. 3 is a view similar to FIG. 1 with the contacts in fully separated position.

FIG. 4 is a View similar to FIG. 2, but with the are shown diagrammatically in a third position.

FIG. 5 is a plan view, partly in section, with the section taken along line 5-5 of FIG. 6 of one end of the arc hood or shield showing the arc suppressing plate in position.

FIG. 6 is a transverse section View taken along line 66 of FIG. 5.

FIG. 7 is a section view similar to FIG. 6 of a second form of the invention.

FIG. 8 is a fragmentary bottom plan view of the second form of the invention, with only the supplementary arc snufling plates inserted.

FIGS. 9 and 10 are detail plan views of the supplementary fiber and metal are snuffing plates, respectively.

Referring to FIGS. l-6 of the drawings, a fixed contact 14 is diagrammatically shown in FIGS. 1 and 3 in relation to a movable contact blade in several different positions of the latter. The fixed contact member may be of usual or conventional shape with oppositely facing jaws or plate portions between which the contact leg 260 of a C-shaped movable contact blade may be inserted and withdrawn. Conveniently, the jaws may be formed by reversely bending the arms of a Ushaped member as shown in my copending application Serial No. 825,744 entitled Arc Hood Supporting Means for Electric Switches, patented May 15, 1962, No. 3,035,140. The invention is not limited to that form of fixed contact member, however. Other forms of contacts may also be used, including butt-type contacts.

The movable contact blade may be a stamped sheet metal part pivoted at the end of the arm 26a about an axis 27 with the leg 260 in position to engage and disengage the fixed contact member 14 as shown in dotted lines in FIGURE 1 and in full lines in FIGURE 3, respectively.

A bail 28 may engage in a recess 262' and pass through similar blade recesses in the blades of adjacent poles of the switch when the invention is applied to a multi-pole switch, for simultaneous movement of the switch blades of all poles.

In moving to engage and disengage the fixed contact, the leg 260 of the movable contact blade is positioned to pass between the parallel legs of one or more U-shaped stamped sheet metal arc suppressing plates 40 of iron, steel or other magnetically conductive metal or alloy. These plates may be placed one above the other in register and held in a slot or slots 37 of an arc hood or shield designated generally by the numeral 30 and made of molded ceramic or phenolic insulating material. The slots may extend inward from one side face of the arc shield.

The shield is also provided with a passage 31 for the switch blade leg 260 to pass through as the blade engages and disengages the fixed contact. The passage 31 extends through the shield from one side to the other transverse to the plate-receiving slots 37 and to the arc-suppressing plates 40.

The arc-suppressing plates are held in the slots 37 by pressing or laterally displacing the ends of parallel extensions 43 and 44 from the plate into engagement with the side walls of the slots. These extensions 43 and 44 extend beyond the transverse portion of the plate and in opposite directions from the plate arms 41 and 42. The extensions have rounded portions near their ends on the outside lateral surfaces to fit into the half-rounded or arcuate grooves 33 and 34'on each side of the slots above ribs or half-rounded fillets 35 which extend from the bottom surface (as viewed in FIGURE 6) and perpendicula-rly upward to the slots. The extensions 43 and 44 of the arc-suppressing plate rest on the tops or inner end surfaces of these fillets at one end while at the opposite end of the plate the ends of legs 41 and 42 rest in similar fashion on similar half-rounded fillets or ribs 36.

From the foregoing, the functions and operation of the invention may be understood.

As the movable contact blade 26c starts to move to open position, it moves from the dotted line position of FIGURE 1 (closed circuit position) to the full line position. An arc will start to be drawn at the instant of separation of the blade arm 26a from the contact 14. The position of the are at the instant of its creation is diagrammatically shown at a in FIGURE 2.

The are acts as a conductor with an electromagnetic field around it which would theoretically be as shown by the large circles around position a (FIGURE 2); but because the arc-suppressing plate or plates are magu netically conductive, the electromagnetic flux is concentrated in them and across the ends of the legs 41 and 42 as shown in fine dotted lines in FIGURE 2. This causes the arc to move at once and rapidly to the position a. Due to the momentum of the arc, it tends to continue beyond that position and to move into the position a as shown in FIGURE 4; but at that point, the theortical field as shown by the large circles is concentrated in the extensions 43 and 44 and across their ends. This creates a force tending to move the are back toward the transverse portion of the arc-suppressing plates and acts similarly on the are products. Thus, while the gases may be vented, the arc and its products, such as hot particles and ionized metallic vapors, are retained in the vicinity of the arc plate and within the arc hood.

It has been noted in actual tests that the amount of discoloration in the housing and adjacent the portions of the hood where the arc gases are vented is less when the invention is employed than when arc plates without the additional extensions 43 and 44 are used. Thus, the

extensions serve dual purposes. On the one hand, they serve to secure and maintain the arc-suppressing plates in proper position while on the other hand they function as means for controlling and directing the play of the arc.

The are snuifing ability can be made even more effective by the addition of a plurality of metallic and insulation plates, alternately stacked above the plates 4% as shown in FIGS. 7-10.

In this form of the invention, the hood 130 (equivalent to hood in FIGS. 1-6) is recessed above (referring to FIG. 7) the arc plates providing a shoulder 132. Into the space above the location of the plates 46, a plurality of U-shaped arc snuffer plates 50, 60, 5% are dropped when the arc hood 130 is inverted from the position in which it appears in FIG. 7.

The plates 50 are stamped from fiber insulation sheet material which has the property of powdering away under the heat of an electric arc and also of tending to suppress the are more quickly. This property has been well known for many years and need not be further explained.

The plates 60 are of similar size and shape as snutfer plates 50, but are stamped from sheet metal such as iron 01' steel or other metal which possesses magnetic conductive properties.

The snufier plates 50 and 60 are of less transverse overall dimension than the arc plates 40 and have no opposite extensions like 44 and 45 of the arc plates. Hence, the plates and 60 can be dropped into the hood with the first dropped, lying upon or against the shoulder 132.

The plates 50 and 60 are inserted alternately with a fiber plate being inserted first. The final insulation plate 50' is inserted in inverted position relative to the other plates which are all placed so that they are in substantial register with the arc plates 40. That is to say, the transverse portion of the plates 50 and 60 overlies the transverse portion of the arc plates 40 and the open ends of all the plates 40, 50, 60 face in the same direction.

After all of the plates 50, 60, 50' are inserted, the arc plates are inserted endwise as described in connection with FIGS. 1-6 and the extensions 44 and 43 are spread. The are plates thus function as before to blow out the are. In addition, in FIG. 7, they hold the snuffer plates 50', 50 and 60 in assembled position.

The reversal of the plate 50' provides an arc chute or passage and partially closes off the arc chamber at the opposite end.

The insulating plates 50 besides spacing the arc plates 60, also confine the are, which is being acted upon magnetically by the plates 60, and help cause it to travel in a predetermined path through the arc chute passage where it can be extinguished.

An angular undercut 134 in the hood 130 directly opposite the arc chute together with the addition of a rib 136 parallel to rib 35 on the porcelain of the hood at each side of the arcing chamber provides additional cooling surface for the hot gases. These ribs also cause turbulence which, along with the magnetic effects due to the shape of the arc and snuli'er plates, tends to retard the expulsion of hot gases and particles.

Many modifications within the scope of the invention will occur to those skilled in the art. Therefore, the invention is not limited to the specific form and configuration of parts as shown and described.

What is claimed is:

1. In an electric switch, fixed and movable contact members, an arc shield overlying said fixed contact member having a passageway therein for exit of arc gases, means to control and direct the movement of an are drawn between said fixed and movable contact members incident to their separation comprising magnetically conductive arc-suppressing plate means having parallel arms in a plane substantially perpendicular to the initial path of the arc and lying on opposite sides of said path, said arms controlling and directing the arc movement in one direction, said shield having slots with an open end into which said plate means are insertable, and extensions from said plate means extending oppositely to said arms which control the movement of the arc and direct it opposite to its first direction after it has passed a predetermined point in traveling in said first direction.

2. In an electric switch, fixed and movable contact members, an arc shield overlying said fixed contact member having a passageway therein for exit of arc gases and a passageway for the movable contact member to enter and engage the fixed contact member, an overhanging portion on said shield adjacent the path of said movable contact member acting as a guard tending to prevent particles generated by the arc and in the venting gases from passing out through said contact-passageway, means to control and direct the movement of an are drawn between said fixed and movable contact members incident to their separation comprising magnetically conductive arc suppressing plate means having parallel arms in a plane substantially perpendicular to the initial path of the arc and lying on opposite sides of said path, said arms controlling and directing the arc movement in one direction, said shield having slots with an open end into which said plate means are insertable, and extensions from said plate means extending oppositely to said arms which control the movement of the arc and direct it opposite to its first direction after it has passed a predetermined point in traveling in said first direction.

3. An electric switch as claimed in claim 1 having a plurality of magnetically conductive plates parallel to and spaced from said are suppressing plate means, said plurality of plates having parallel transversely connected arms extending in the same direction as and in substantial register with the arms of said arc-suppressing plate means, and means to prevent arc movement inwardly of the arms of said plurality of plates past their transverse connection.

4. An electric switch as claimed in claim 1 having a plurality of magnetically conductive plates parallel to said arc-suppressing plate means, said plurality of plates having parallel arms transversely connected extending in the same direction as and in substantial register with the arms of said arc-suppressing plate means, insulating means spacing said plate means apart and from said arc-suppressing plate means, said insulating means preventing arc movement inwardly of the arms of said plurality of plates past their transverse connection.

5. An electric switch as claimed in claim 4 wherein the insulating means comprise plates similar in shape to said plurality of magnetic plates and are stacked alternately with the latter.

6. An electric switch as claimed in claim 5 wherein the insulating plate next to said arc-suppressing plate means is positioned reversely with respect to its neighbor.

7. An electric switch as claimed in claim 1 wherein said shield has passageways from opposite faces of said aresuppressing plate means for exit of arc gases, means to provide increased cooling surfaces and to create turbulence of the hot gases leaving said passageways comprising an overhang adjacent one passageway and a plurality of substantially parallel r-ibs adjacent another passageway.

8. An electric switch as claimed in claim 1 having a plurality of magnetically conductive plates parallel to and spaced from said arc-suppressing plate means, said plurality of plates having parallel transversely connected arms extending in the same direction as and in substantial register with the arms of said arc-suppressing plate means, and means on said shield engaged by said extensions when spread to hold said arc-suppressing plate means in place, the latter also holding said plurality of plates in place.

9. An electric switch as claimed in claim 1 having a plurality of insulation plates and a plurality of magnetically conductive plates both having parallel trans versely connected arms extending in the same direction and in substantial register with the arms of said arc-suppressing plate means, and an additional insulating plate between said pluralities of plates and said arc-suppressing 20 plate means, said additional plate being reversely positioned with respect to its neighbor.

10. An electric switch as claimed in claim 1 having a plurality of insulation plates and a plurality of magnetically conductive plates both having parallel transversely connected arms extending in the same direction and in substantial register with the arms of said arc-suppressing plate means, and an additional insulating plate between said pluralities of plates and said arc-suppressing plate means, said additional plate being reversely positioned with respect to its neighbor, and means on said shield engaged by said extensions when spread to hold said arc-suppressing plate means in place, the latter also holding said plurality of plates in place.

References Cited in the file of this patent UNITED STATES PATENTS 

